It is a question of CHOICE. I can choose to let some a**hole get away with a bad attiude or I can hospitalize the SOB. Aikido gives me a variaty of options where as harder styles are more "punch in his nose firts, ask questions later" way of thinking.

In the dojo it is not so different , I can choose to ease Uke to the matt giving him all the time he needs to adjust himself, or I can slam him down with an extra 'twist'.

I choose to do so according to the way I feel Uke's energy and if he is, junior or a veterain, young or old, "hot" or "cold". The energy I get dictates my reaction. In the street you have to assess the situation and get the energy of the oponent in order to decide the amount of actual danger you are in and so to decide the damage to inflict.